JP4854969B2 - Novel storage material having nanoporous carbon structure and method for producing the same - Google Patents

Description

  The present invention relates to an occlusion material having a nanoporous carbon structure that can occlude and adsorb a hydrocarbon gas such as methane, and a method for producing the same. More specifically, the present invention has a layer of carbon in which the distance between layer planes is larger than that of ordinary graphite, and a portion for maintaining the interlayer distance of these layers is selectively maintained by the carbonized material. And a production method of the occlusion material having a nanoporous carbon structure having a wide lipophilic surface and having a carbon layer suitable for occlusion of hydrocarbons such as methane, and having a layer-to-layer distance suitable for occlusion Regarding the method.

  Methane is a primary energy source with an enormous amount of accumulation on the earth, and is expected to be a promising next-generation energy source for preventing global warming in that it emits less carbon dioxide than other existing fuels. Has been. In particular, there are methane hydrate belts that lie on the sea floor in the sea near Japan, and the use of methane as an energy source in Japan, which lacks other energy sources, is an important issue for future energy policy. It has become.

  By the way, when methane is used as energy for automobiles or transported by ship from the seabed or overseas production areas to use areas, it is necessary to store the methane. So far, as a method of storing methane, a method of cooling to a low temperature state of −160 ° C. or lower, or applying a high pressure of 20 MPa or higher has been performed, but the energy consumption is high and the cost is increased. , There was a drawback of poor handling. In order to overcome these disadvantages, an adsorption storage method using a gas concentration phenomenon to a porous solid and an occlusion method using methane hydrate that becomes a solid state at a pressure of several MPa near 0 ° C. are studied. Has been. For example, a gas storage material such as methane (see Patent Document 1) made of a cylindrical structure having a diameter of 10 nm to 600 nm in which graphite nanofiber crystals are laminated, and an inorganic layered substance having a positive layer charge such as hydrotalcite Hydrocarbon occlusion material obtained by carbonizing by inserting an organic anion between them (see Patent Document 2), gas adsorbing material obtained by reacting copper ions and trimesic acids (see Patent Document 3), and methane as methane class A method of storing as a rate hydrate (see Patent Document 4) has been reported.

Among the adsorbents known so far, the amount of methane stored in activated carbon is said to be the largest, but the pore structure of activated carbon contributes to adsorption storage by van der Waals force of molecules such as methane. In addition to micropores with a diameter of 2 nm or less, there are useless spaces such as mesopores with a diameter of more than 2 nm and macropores with a diameter of 50 nm or more that do not contribute much to methane storage. Increasing the structure that contributes to storage is a challenge for increasing methane storage. As an improvement technique of such activated carbon, for example, a gas such as methane made of activated carbon obtained by pressure molding without adding a binder to a raw material such as powdered or granular cellulose or polyimide compound, and carbonizing this. There are storage materials (see Patent Document 5). In addition, the present inventors have also developed a methane adsorbing material comprising an oxidation product obtained by oxidizing a porous carbon material such as activated carbon (see Patent Document 6).
In addition, many reports have been made on methane gas and natural gas storage methods using conventional methane storage materials such as zeolite, activated carbon, and silica gel (see Patent Documents 7 and 8, etc.).

In addition, for layered clay such as montmorillonite, alumina, zirconia, chromium oxide, titanium oxide, SiO ₂ —TiO ₂ , SiO ₂ —Fe ₂ O ₃ , Al ₂ O ₃ —SiO _2, etc. are intercalated between the layers. It is known that an interlayer cross-linked porous body is formed (see Non-Patent Document 1), and hydrogen or hydrocarbons are occluded in such a layered structure and used as a fuel supply source. Yes.
As a carbonaceous layered material, graphite is well known. Graphite is a material having a strongly anisotropic layered structure with a distance between layer planes of 0.335 nm. Such strong anisotropy has a large effect on the reactivity, and reactions that attack in-plane bonds are unlikely to proceed, but reactions that insert reactants while expanding the layers, so-called intercalation This forms a graphite intercalation compound. For example, a gas storage material such as methane using a graphite intercalation compound obtained by adding cesium or rubidium to a carbon-based material such as graphite (see Patent Document 9) has been reported.
However, despite the fact that graphite has a layered structure similar to layered clay, only relatively small molecules such as alkali metals and halogens can form graphite intercalation compounds, and graphite or graphite intercalation compounds have a large surface area. Even if it did not constitute a porous body and attempted to form a cross-link by subsequent heat treatment, it was difficult to collapse and form a stable pore.

On the other hand, according to the results of theoretical calculations such as simulation, it has a pore wall equivalent to one layer of graphite, and has a size (about 0.7 to 0.8 nm) enough to allow two molecules of methane to enter between layers. Occupants have been shown to be ideal for methane storage. However, there is no research that actually tried to synthesize such an ultimate occlusion body.
In order to obtain a porous carbon material having an ideal layer structure, the inventors dispersed graphite oxide obtained by oxidizing graphite in an alkali, and further expanded the layer with long-chain organic molecules. Thus, it has been shown that a carbon-containing porous composite material having a high surface area can be produced by introducing a hard crosslinking agent such as a metal or metalloid oxide (see Patent Document 10). Further, by carbonizing such a high surface area carbon-containing porous composite material at a higher temperature and further eluting the metal (semimetal) oxide with hydrofluoric acid or the like, a mesoporous carbon structure having a specific surface area of 700 m ² / g or more. It has been shown that a body can be manufactured (see Patent Document 11). Carbonization of the carbon-containing compound between the carbon layer and the carbon layer in order to maintain a carbon layer having a fixed interplanar distance before eluting the metal (metalloid) oxide with hydrofluoric acid or the like It has been found that by providing a process for forming a treated product, a novel carbon-based hydrocarbon storage material having a thin wall and suitable for storing hydrocarbons such as methane can be produced (see Patent Document 12). However, the thickness of the carbon layer and the size of the surface area that can be effectively used are not sufficient.

JP 2001-212453 A JP 2002-28481A JP 2002-204953 A JP 2003-3181 JP 2001-287905 A JP 2003-144917 A JP 2003-28397 A JP 2003-35399 A JP 2001-287907 A JP 2003-192316 A JP 2004-210583 A Japanese Patent Application No. 2003-205003 "Surface", Vol. 27, No. 4 (1989), 290-300

According to the results of theoretical calculations such as simulation, an occlusion body that has a pore wall equivalent to one layer of graphite and has a pore size that fits between two layers of methane just between the layers is an ideal structure for methane storage. Therefore, it is desired to provide a graphite-like material having such an ideal structure, that is, a carbonaceous layered material.
The present invention has been made for the purpose of creating an ideal occlusion material for storing hydrocarbons such as methane by a soft chemical method using graphite having a single atomic layer as a starting material. For this purpose, the present inventors have expanded the interlayer of graphite using a compound of at least one metal or metalloid selected from silicon, aluminum, titanium, zirconium and iron, and carbon-containing compounds. Of the hydrocarbon occlusion material having a carbon layer in which the distance between the layer planes is larger than that of normal graphite, and these layers are maintained by the carbonized compound carbonized product. A manufacturing method has been developed (see Patent Document 12). However, the hydrocarbon storage material produced by this method is not sufficient in terms of the thickness of the carbide used as the cross-linking material and the size of the surface area that can be effectively utilized, and the development of higher performance materials is desired. It was rare.

The inventors of the present invention have a hydrocarbon occlusion material (see Patent Document 12) in which the expanded graphite layer is maintained by a carbonized compound carbonized product, and can take a wide range of carbonized product thickness and carbon lipophilic surface. That was not enough. As a result of intensive studies on this cause, it was assumed that it might be due to adhesion of a large amount of carbonized material by carbonization. However, if the amount of the carbonized material is reduced, it becomes difficult to maintain the interlayer structure, and the layer structure itself becomes unstable, so it is extremely difficult to reduce the amount of the carbonized material.
In order to solve this problem, many techniques have been tested, and at least one metal or metalloid selected from among silicon, aluminum, titanium, zirconium and iron that maintains an expanded graphite layer. It was possible to establish a method for selectively forming a carbonized product on the surface portion of the compound. According to this method, the carbonized material is applied to the surface portion of at least one metal or metalloid compound selected from silicon, aluminum, titanium, zirconium and iron that maintains the expanded graphite layer. Nanoporous carbon structure that is formed selectively, and carbonized products do not adhere to the excess part such as the surface part of the graphite layer, so that the thickness of the graphite layer is maintained as it is and the lipophilic surface of carbon that can be effectively used can be taken large Found that the body can be obtained.

That is, the present invention includes (1) a step of oxidizing graphite to make a graphite oxide, (2) a step of fixing the distance between layer surfaces of the graphite oxide, and (3) a distance between fixed layer surfaces. A step of adding a hydroxy hydrocarbon compound between the carbon layer and the carbon layer in order to maintain a carbon layer having (4) a material having a fixed inter-layer distance and the step (3) (5) a step of removing the unreacted hydroxy hydrocarbon compound, (6) a step of carbonizing the remaining hydroxy hydrocarbon compound to obtain a carbonized product, and ( 7) a step of removing the material that fixes the distance between the remaining layer surfaces, and a layer of carbon in which the distance between the layer surfaces is larger than that of normal graphite, and these layers are carbonized. Ri method of manufacturing a storage material having a nanoporous carbon structure characterized in that it is maintained.
Further, the present invention is characterized by having a carbon layer in which the distance between the layer surfaces is larger than that of ordinary graphite, and the interlayer distance between these layers is maintained by a carbonized material having a very thin layer. The present invention relates to an occlusion material having a nanoporous carbon structure.

The occlusion material having the nanoporous carbon structure of the present invention has a carbon layer in which the distance between layer planes is larger than that of normal graphite, and these layers are made of a metal (half-layer) using a hydroxy hydrocarbon compound. Generated by selectively forming a very thin layer on the surface of the metal (semi-metal) compound part that maintains the interlayer distance of the carbon-containing composite using the metal) compound as a cross-linking agent and carbonizing it. It is characterized in that it is maintained by an extremely thin carbonized product (carbonized structure).
The method for producing an occlusion material having a nanoporous carbon structure according to the present invention includes (1) a step of oxidizing graphite to form a graphite oxide, (2) a step of fixing the distance between layer surfaces of the graphite oxide, and (3) a step of adding a hydroxy hydrocarbon compound between the carbon layer and the carbon layer in order to maintain a carbon layer having a fixed inter-layer distance, and (4) fixing the inter-layer distance. A step of reacting the material with the hydroxyhydrocarbon compound added in the step (3), (5) a step of removing the unreacted hydroxyhydrocarbon compound, and (6) carbonizing the remaining hydroxyhydrocarbon compound. A carbonized product, and (7) a step of removing the material that fixes the distance between the remaining layer surfaces.
More specifically, (1) as a first step, first, graphite is oxidized to obtain a graphite oxide, and (2) as a second step, the interlayer of the graphite oxide is treated by a soft chemical technique to obtain a layer surface. Then, the porous graphite composite material is obtained by fixing the distance between them, and (3) as a third step, a hydroxy hydrocarbon compound is further added to the pore space of the porous composite to allow hydroxy carbonization between the layers. Hydrogen is introduced, and (4) in the fourth step, the material consisting of the metal or metalloid compound in which the distance between the layer surfaces is fixed is reacted with the hydroxy hydrocarbon compound added in the third step, thereby reducing the distance between the layer surfaces. The immobilized metal or metalloid compound and the hydroxy hydrocarbon compound are bonded, preferably covalently bonded and fixed. (5) As the fifth step, the unimmobilized unfixed (6) Next, a sixth step is carried out by selectively removing the hydroxyhydrocarbon compound by washing and removing the hydroxyhydrocarbon compound selectively in the portion of the material made of the metal or metalloid compound that fixes the inter-layer distance. As above, the hydroxy hydrocarbon compound selectively remaining in the part is carbonized at a high temperature to obtain a carbonized product. (7) And as the seventh step, the remaining inter-layer distance other than carbon is fixed with concentrated acid. The material comprising the metal or metalloid compound that has been converted can be removed to finally produce an occlusion body having a nanoporous carbon structure with a carbon wall as thin as graphite.

The first step and the second step in the method for producing the carbon-based hydrocarbon storage material of the present invention described above are the same methods as those described in Patent Document 10 relating to the porous graphite composite material. The third step of adding a compound to be carbonized, the sixth step for forming a carbonized product, and the seventh step of removing materials other than carbon with concentrated acid are almost the same as the method described in Patent Document 11. Is the method.
As a specific example of the second step of the present invention, at least one metal or metalloid selected from silicon, aluminum, titanium, zirconium and iron is interposed between the graphite oxides produced in the first step. It includes intercalating a compound sol or polynuclear metal cation and then heat treating it in an inert atmosphere to form a metal or metalloid oxide. Furthermore, if necessary, a treatment step with a surfactant containing a long-chain alkyl group can be included.
In the third step of the present invention, a pillar mainly composed of at least one metal or metalloid compound selected from silicon, aluminum, titanium, zirconium and iron is formed between the layers of the graphite oxide layered body. The porous graphite composite material is subjected to a treatment capable of further producing a carbonized compound of a carbon-containing compound on the pore space, particularly on the surface of the metal (semimetal) oxide serving as a pillar. The process uses a hydroxy hydrocarbon compound that is reactive with at least one metal or metalloid compound selected from silicon, aluminum, titanium, zirconium and iron, rather than any carbon-based compound that can be carbonized. It is characterized by this.

The sixth step of the method of the present invention is a step of carbonizing the hydroxy hydrocarbon to produce a carbonized product (carbonized structure). The carbonization treatment can be performed by heat treatment at 100 ° C. to 1000 ° C., although it depends on the material used. More specifically, the carbonization is performed at a high temperature of 100 ° C. or higher, preferably 550 ° C. or higher, 650 ° C. or higher, 700 ° C. or higher, more preferably 550 to 1000 ° C. or 700 to 1000 ° C. in an inert atmosphere. The high temperature treatment is preferably performed in an inert atmosphere, and the inert atmosphere may be a state in which carbon atoms are not affected by oxidation or the like, for example, in vacuum, nitrogen, argon, helium, etc. In the presence of an inert gas. The treatment time is usually about 1 to 10 hours, 1 to 8 hours, preferably about 2 to 5 hours.
The seventh step of the method of the present invention is a treatment for eluting metal oxide or metalloid oxide from the carbonized porous graphite composite material at high temperature. The elution treatment can be performed using a substance that can elute metal oxide or metalloid oxide other than carbon. Preferable substances include strong acids such as hydrofluoric acid (HF). For example, it can be carried out by immersing the porous graphite composite material in an aqueous solution of a substance capable of eluting metal oxide or metalloid oxide. The treatment temperature is not particularly limited and depends on the properties of the substance that can be eluted, but may be room temperature, heating, or cooling, and can usually be performed at room temperature. After completion of the elution treatment, it is sufficiently washed with purified water such as distilled water and dried in the air at 60 ° C to 120 ° C.

The porous graphite composite material used as the raw material for the third step of the present invention includes at least one metal or metalloid selected from silicon, aluminum, titanium, zirconium and iron between the layers of the graphite oxide layered body. A porous graphite composite material in which a pillar mainly composed of the above compound is formed is preferable. Such a porous graphite composite material can be manufactured by the method described in Patent Document 10. That is, after oxidation of graphite into an oxide layered body, a sol or polynuclear metal positive electrode of at least one metal or metalloid compound selected from silicon, aluminum, titanium, zirconium and iron is interposed between the layers. The ions can be intercalated and then heat treated in an inert atmosphere.
More specifically, the graphite oxide layered product is prepared by, for example, immersing graphite in a mixed solution of concentrated sulfuric acid and nitric acid and adding potassium chlorate to react, or in a mixed solution of concentrated sulfuric acid and sodium nitrate. It is prepared by soaking, adding potassium permanganate and reacting. By these treatments, the carbon atoms of graphite change from the sp ² state to the sp ³ state, and change from a state like a carbon atom forming a so-called benzene ring to a saturated aliphatic carbon atom state. An oxygen atom, a hydrogen atom, or the like is bonded to the changed carbon atom, and an oxygen atom can be introduced between the layers.
Next, in the same manner as the method for producing a well-known clay interlayer crosslinked porous material between the layers of the graphite oxide layered material produced as described above, from among silicon, aluminum, titanium, zirconium and iron. A pillar made of a compound of at least one selected metal or metalloid is formed. As a method for forming such a pillar, a sol of the metal or metalloid compound is introduced between layers, and then this is heated in an inert atmosphere to form a stable pillar. For example, a semi-metallic polynuclear metal cation is introduced between the layers and then heat-treated in an inert atmosphere to form a stable pillar.

For example, a mixed sol such as silica sol, alumina sol, titania sol, zirconia sol, silica-titania sol, silica-iron oxide sol, alumina-silica sol is introduced between the layers of the graphite oxide layered body, and then heat-treated in an inert atmosphere. For example, a porous composite material including a stable pillar made of an oxide of a metal or a semimetal, or a mixed oxide thereof can be obtained.
Moreover, as a method using a polynuclear metal cation, for example, [Al ₁₃ O ₄ (OH) ₂₄ ] ⁷⁺ , [Zr ₄ (OH) ₈ (H ₂ O) ₁₆ ] ⁸⁺ , [Fe ₃ O (OCOCH ₃ ) ₆ ] There is a method in which ⁺ or the like is introduced between the layers of the graphite oxide layered body and then heat-treated in an inert atmosphere to form pillars of alumina, zirconia, iron oxide, or the like.
In any of these methods, the heat treatment needs to be performed in an inert atmosphere, for example, in a vacuum or in a nitrogen or argon stream in order to prevent the carbon constituting the graphite from being oxidized. In this case, the heating condition is 120 ° C. or higher, preferably 500 to 700 ° C., and the heating time is usually 2 to 8 hours.

The pillar formed between the layers of the graphite oxide layer thus formed is a compound of at least one metal or metalloid selected from silicon, aluminum, titanium, zirconium and iron, ie, silicon-containing It is composed of a compound, an aluminum-containing compound, a titanium-containing compound, a zirconium-containing compound, an iron-containing compound, or any combination thereof.
The content of the metal or metalloid compound in the porous graphite composite material thus produced is in the range of 5 to 95% by mass, preferably 50 to 70% by mass. The graphite oxide layer and the left and right pillars form pores having a pore diameter of 0.6 to 2.5 nm.

  Another method for forming a graphite porous structure is to first intercalate ions or molecules for intercalation into a graphite oxide layer, and then from among silicic acid, aluminate, titanic acid and zirconic acid. There is a method of forming a stable pillar made of a compound of silicon, aluminum, titanium or zirconium by introducing an ester of a selected inorganic polybasic acid and a lower alkanol and heat-treating it in an inert atmosphere. .

As an ion for interlayer expansion used in this case, for example, the following general formula (1)
[R ¹ -NR ² R ³ R ⁴ ] ⁺ (1)
(In the formula, R ¹ is a long-chain alkyl group having 8 to 20 carbon atoms, R ² , R ³ and R ⁴ are each an alkyl group having 1 to 3 carbon atoms, and one of these groups is R ^1. May be the same.)
And quaternary compound cations having a long-chain alkyl group represented by the formula:
Examples of R ¹ in the general formula (1) include long-chain alkyl groups having 8 to 20 carbon atoms such as octyl group, nonyl group, decyl group, dodecyl group, hexadecyl group, and octadecyl group. Examples of ² , R ³ and R ⁴ include an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, and a provir group. One of R ^{2 to} R ^{4 in} the general formula (1) may optionally be the same as R ¹ , but if a long chain alkyl group is further included, the graphite oxide layered body It becomes difficult to introduce between layers (see Patent Document 10).
In addition, as in the case of the clay-cross-linked porous body, these are those in which cations are inserted between the layers to expand the layers, but in the case of graphite oxide, the surface of the layer releases protons and becomes acidic. For example, the following general formula (2)
NR ⁵ R ⁶ R ⁷ (2)
(In the formula, at least one of R ⁵ , R ⁶ and R ⁷ is an alkyl group having 1 to 3 carbon atoms or a hydroxyalkyl group having 1 to 3 carbon atoms, and the remainder is a hydrogen atom)
Similarly, a molecule such as an organic amine represented by can be used to extend the interlayer (see Patent Document 10).

As a method for introducing such intercalation ions or molecules, for example, in an alkaline aqueous solution, 8 to 36.0 times the amount of intercalation ions or molecules is added to the graphite oxide layered body based on its mass, and the room temperature is increased. From 90 to 90 ° C. for 15 to 60 minutes.
This graphite oxide is further reinforced by simply inserting such intercalation ions or molecules between the layers, which may cause decomposition or desorption when heat-treated, resulting in no formation of pores. Processing may be required.
This is because the interlayer of the graphite oxide is expanded by ions or molecules for interlayer expansion, and further, a metal or semi-metal inorganic polybasic acid selected from silicic acid, aluminate, titanic acid and zirconic acid is interposed between the layers. After introducing an ester with a lower alcohol, drying is carried out at 50 to 70 ° C., followed by heat treatment at 500 to 700 ° C. for 2 to 8 hours in an inert atmosphere. The above-mentioned inorganic polybasic acid ester is hydrolyzed or decomposed by a subsequent heat treatment to provide a stable compound having a strength capable of supporting the interlayer, that is, a solid silicon-containing compound, aluminum-containing compound, titanium-containing compound. Any compound or zirconium-containing compound may be used.
In the case of metals, these compounds are metal oxides, and nitrides, carbides, and the like are by-produced depending on the type of atmospheric gas and heating conditions. In the case of a semimetal such as silicon, examples in which an alkoxy group is removed to form oxygen or a hydroxyl group, and those in which a lower alkyl group is bonded thereto can be mentioned. The amount of these inorganic polybasic acid esters used is selected in the range of 20 to 100 times, preferably 40 to 80 times the mass of the graphite oxide layered product.

In order to introduce this inorganic polybasic acid ester, an intercalation compound obtained by intercalating ions or molecules for intercalation expansion into a graphite oxide layered body is added to a predetermined amount of the inorganic polybasic acid ester. At this time, if desired, an organic solvent such as dimethylformamide, acetone, benzene, toluene or the like can be used, or the reaction can be promoted by heating to a temperature of 40 to 80 ° C.
After the reaction, the solid is separated from the reaction mixture, washed with a solvent such as ethyl alcohol, and then dried by air drying, vacuum drying, freeze drying or heating. By this treatment, an intercalation compound in which the inorganic polybasic acid ester is inserted between the intercalation ions or molecules of the graphite oxide layered body is obtained.

Next, when this intercalation compound is heated and decomposed, a stable pillar composed of a compound of silicon, aluminum, titanium or zirconium is formed between the interlaminar layers. The heating at this time may be performed in an inert atmosphere, for example, under an inert gas such as nitrogen or argon, or under vacuum conditions in order to prevent the carbon constituting the base material from being oxidized. is necessary. The heating temperature is 120 ° C. or higher, preferably in the range of 500 to 700 ° C. The heating time is usually 2 to 8 hours.
In this way, a porous graphite composite material having an average particle size of 0.6 to 2.5 nm and a specific surface area of 400 to 1500 m ² / g is obtained.

In the method for producing an occlusion material having a nanoporous carbon structure according to the present invention, a fourth step and a fifth step are further added to the first step, the second step, the third step, the sixth step, and the seventh step. It is characterized by that.
Further, the present invention provides at least one selected from silicon, aluminum, titanium, zirconium and iron used as a material for fixing the interlayer distance as a material for forming the carbonized product in the third step. A hydroxy hydrocarbon compound having reactivity with a metal or metalloid compound is used as the compound.
As such hydroxy hydrocarbons, those having a high boiling point are preferable because a reaction for forming a bond, preferably a covalent bond, is performed at a relatively high temperature, and those having a low boiling point such as ethyl alcohol can be volatilized. This is not preferable because of its properties. In addition, a compound having a high carbon content is preferable in order to perform carbonization in a later step. Examples of the hydroxy hydrocarbon of the present invention include compounds in which one or two or more hydroxyl groups are bonded to a hydrocarbon group having 5 to 50 carbon atoms, preferably 5 to 30 carbon atoms. Functional groups other than hydroxyl groups such as carboxyl group, ester group, carbonyl group, ether group, amino group, nitro group and halogen atom may be bonded. There is no need to use the one to which the group is attached. In addition, amino groups and halogen atoms are not preferred because toxic gases may be generated during carbonization.
It is sufficient that one hydroxyl group is attached, but two or more hydroxyl groups may be bonded, but an inexpensive one is preferable from the viewpoint of cost.
As the hydrocarbon group in the hydroxy hydrocarbon compound of the present invention, a linear or branched alkyl group having 5 to 50 carbon atoms, preferably 5 to 30 carbon atoms, a straight chain having 5 to 50 carbon atoms, preferably 5 to 30 carbon atoms. Chain or branched alkenyl group, linear or branched alkynyl group having 5 to 50 carbon atoms, preferably 5 to 30 carbon atoms, monocyclic or polycyclic group having 6 to 50 carbon atoms, preferably 6 to 30 carbon atoms Substituted with a cyclic or condensed cyclic aromatic group, 7 to 50 carbon atoms, preferably 7 to 30 monocyclic, polycyclic or condensed cyclic alkyl, alkenyl or alkynyl groups Examples thereof include an aromatic group, a monocyclic, polycyclic or condensed cyclic aralkyl group having 7 to 50 carbon atoms, preferably 7 to 30 carbon atoms. Preferred hydrocarbon groups are monocyclic, polycyclic or condensed cyclic aromatic groups having 6 to 50 carbon atoms, preferably 6 to 30 carbon atoms, and monocyclic rings having 7 to 50 carbon atoms, preferably 7 to 30 carbon atoms. And an aromatic group substituted with a formula, polycyclic, or condensed cyclic alkyl group. Preferred hydroxy hydrocarbon compounds include α-naphthol, β-naphthol, 2,3-dihydroxynaphthalene, hydroxy-biphenyl, phenol and the like.

As a method for adding the hydroxy hydrocarbon in the third step of the present invention, a method such as a normal impregnation method or a dipping method is used. For example, a method of impregnating the porous graphite composite material obtained in the second step in a hydroxy hydrocarbon solution can be mentioned. The solvent is preferably a volatile solvent that can dissolve hydroxy hydrocarbons. For example, ketone solvents such as acetone and methyl ethyl ketone, and ether solvents such as diethyl ether and diglyme are preferable. These solvents are preferably substantially anhydrous and degassed with an inert gas such as nitrogen gas.
The amount of the hydroxy hydrocarbon compound used is preferably in the range of 1: 0.1 to 1:10, preferably about 1: 0.2 to 1: 3, based on the mass of the raw porous graphite composite material. . Although the concentration of the hydroxy hydrocarbon solution can be used in a wide range, it is usually 20 to 80% by mass, preferably about 30 to 60%.
The treatment temperature is not particularly limited as long as it is room temperature or higher. Although it may be heated, it is usually only allowed to stand at room temperature. The impregnation time is not particularly limited and may be allowed to stand for several days, but is usually 10 to 40 hours, preferably about 10 to 20 hours.
After the hydroxy hydrocarbon is added, the solvent used is removed. Usually, the solvent is distilled off under normal pressure or reduced pressure. Therefore, it is preferable to use a volatile solvent that can be easily distilled off.

  In the fourth step of the present invention, the material comprising at least one metal or metalloid compound selected from silicon, aluminum, titanium, zirconium and iron fixing the inter-layer distance is used in the third step. This is a step of reacting the added hydroxy hydrocarbon compound to bond, preferably covalently bond, and fix the metal or metalloid compound and the hydroxy hydrocarbon compound that have fixed the distance between the layer surfaces. The immobilization may be a physical method such as adsorption or intermolecular force, but a chemical method such as a covalent bond is preferable because it allows for more reliable immobilization. As the immobilization by a covalent bond, various chemical methods such as esterification with a metal or metalloid compound, etherification, and acid anhydride can be adopted, but esterification is simple and preferable. Esterification can be performed in a relatively short time by heating to a high temperature. A compound particularly suitable for such esterification includes a silicon compound. Silicon compounds can complete esterification in a relatively short time. For example, by treating at about 100 to 400 ° C., preferably about 200 to 350 ° C. under an inert gas atmosphere such as nitrogen gas, for about 0.5 to 3 hours, 1 to 2 hours, The esterification can be completed. Further, if necessary, a catalyst such as an acid or an alkali may be added. However, since subsequent washing is required, it is preferable to carry out at a high temperature without a catalyst.

In the fifth step of the present invention, unreacted unreacted hydroxyhydrocarbon compound is removed, and hydroxyhydrocarbon is selectively added to a portion of the material composed of a metal or a semimetal compound in which the distance between layer surfaces is fixed. It is a process of leaving it.
This step is performed by dissolving the hydroxy hydrocarbon compound and washing with a volatile solvent, preferably in an inert gas atmosphere such as nitrogen gas. As the solvent, various solvents used in the third step described above can be used. It may be simply immersed in such a solvent, or may be washed by stirring in a large excess of solvent.
After washing, it is preferable to dry under normal pressure or reduced pressure in order to remove the solvent used.

The sixth step of the present invention is a step of carbonizing the hydroxy hydrocarbon compound selectively remaining in the portion at a high temperature to obtain a carbonized product.
The carbonization treatment to produce a carbonized product (carbonized structure) by carbonization treatment depends on the type of the hydroxy hydrocarbon compound used, but is usually 100 ° C to 1000 ° C, preferably 500 ° C to 1000 ° C. It can be done by processing. More specifically, the carbonization is performed at a high temperature of 100 ° C. or higher, preferably 550 ° C. or higher, 650 ° C. or higher, 700 ° C. or higher, more preferably 550 to 1000 ° C. or 700 to 1000 ° C. in an inert atmosphere. The high temperature treatment is preferably performed in an inert atmosphere, and the inert atmosphere may be a state in which carbon atoms are not affected by oxidation or the like, for example, in vacuum, nitrogen, argon, helium, etc. In the presence of an inert gas. The treatment time is usually about 1 to 10 hours, 1 to 8 hours, preferably about 2 to 5 hours. This carbonization treatment may be performed once, but may be repeated twice or more as necessary.

The carbonized porous graphite composite material thus produced is treated in the seventh step of the present invention. The seventh step of the present invention is a treatment for eluting metal oxide or semimetal oxide from the carbonized porous graphite composite material. The elution treatment can be performed using a substance that can elute metal oxide or metalloid oxide other than carbon. Preferable substances include strong acids such as hydrofluoric acid (HF). For example, it can be carried out by immersing the porous graphite composite material in an aqueous solution of a substance capable of eluting metal oxide or metalloid oxide. The treatment temperature is not particularly limited and depends on the properties of the substance that can be eluted, but may be room temperature, heating, or cooling, and can usually be performed at room temperature. After completion of the elution treatment, it is sufficiently washed with purified water such as distilled water and dried in the air at 60 ° C to 120 ° C.
The carbon-based hydrocarbon storage material of the present invention thus produced can be used as it is, but it is degassed at 600 ° C. to 1200 ° C., preferably 800 ° C. to 1000 ° C., preferably under reduced pressure. The pore can be activated by performing the above.

The occlusion material having a nanoporous carbon structure of the present invention is a carbonization of a hydroxy hydrocarbon that is selectively bonded to a surface portion of a metal or metalloid compound that has maintained the interlayer distance of the porous graphite composite material described above. The metal oxide or metalloid oxide that has formed pillars is eluted by forming a treated product (carbonized structure) and then eluting the metal oxide or metalloid oxide, and has a thin carbon wall. Thus, a structure having a large specific surface area is formed. Therefore, the occlusion material having a nanoporous carbon structure according to the present invention does not maintain the carbon layer structure by the formation of pillars by a metal oxide or a semimetal oxide, and the hydroxy hydrocarbon compound produced by carbonization treatment It is considered that the carbon layer structure is maintained by the carbonized product (carbonized structure).
Such a carbon layer structure may be one in which the carbon layers are regularly arranged, and each layer is randomly present in a three-dimensional disordered state, such as a card house. You may do. The occlusion material having a nanoporous carbon structure of the present invention maintains a constant layer interval expanded by the action of intercalation of a surfactant or the like by a carbonized product (carbonized structure) generated by carbonization. It is considered that the layer structure of the carbon rearranged in FIG. The pore size of the occlusion material having the nanoporous carbon structure of the present invention is about 0.6 to 4.2 nm, preferably about 0.7 to 4.0 nm, and has a large specific surface area.

Conventionally, intercalation and pillaring methods have been generally used to make clays and layered metal oxides porous, but such methods should be applied directly to graphite with neutral walls. I could not. The present inventors converted graphite into an ionic carbon layered compound (graphite oxide, hereinafter referred to as GO) having a swelling property similar to that of clay by liquid phase oxidation, and applied a soft chemical technique thereto. Thus, a unique method has been provided in which a crosslinked silica is inserted between carbon layers, and then the layers are returned to graphene properties again by a technique such as carbonization. By applying “dispersion / interlayer pre-expansion-hydrolysis method” to graphite oxide (GO), it is possible to create a graphic porous composite with a silica network structure (Nanoporous Graphitic Composite, named NPGC) The composite has a high specific surface area (> 1000 m ² / g) and has an affinity for water between the carbonaceous solid and the silica, so that it has not only a gas occlusion body but also a special adsorbent. It was expected to be applied as a catalyst.
Furthermore, in the present invention, in order to improve the affinity for an organic fuel gas such as methane, addition of a thin thickness is performed by the procedure of interlayer organic polymer modification / selective esterification of silica surface-carbonization-silica elution using NPGC as a template. This is the first successful synthesis of a novel nanoporous layered carbon compound with carbon cross-linked. The present invention provides a carbon-based hydrocarbon storage material suitable for storing hydrocarbons such as methane, and a method for producing the same.

Next, the occlusion material having a nanoporous carbon structure of the present invention will be described based on specific examples, but the occlusion material having a nanoporous carbon structure of the present invention is not limited to these specific examples.
Graphite was oxidized by the method of Staudenmehr (L. Staudenmier, Ber Deutsche Chem. Ges. 1989, 31, 1481.) to produce graphite oxide (hereinafter referred to as GO). A GO (hereinafter referred to as GOC ₁₆ ) in which hexadecyltrimethylammonium ion (chemical formula: CH ₃ (CH ₂ ) ₁₅ N ⁺ (CH ₃ ) ₃ ) was intercalated with this GO was produced. A porous graphite composite material (hereinafter referred to as GOC ₁₆ T) obtained by treating this GOC ₁₆ with tetraethoxysilane (referred to as TEOS) was produced.
The obtained GOC ₁₆ T was heat-treated at 550 ° C. under vacuum or in a helium gas atmosphere for 2 hours. The obtained product is hereinafter referred to as NPGC (Nanoporous Graphitic Composite).

The NPGC obtained here had a specific surface area of 870 m ² / g. This was vacuum pretreated at 550 ° C. for 2 hours, cooled to room temperature, and then impregnated with an acetone solution of 2,3-dihydroxynaphthalene overnight. Thereafter, acetone was distilled off, and an esterification reaction was carried out at 300 ° C. in a nitrogen atmosphere for 1 hour. Subsequently, after washing with acetone to remove excess hydroxynaphthalene compound and drying, carbonization was performed at 700 ° C. for 2 hours in vacuum. Finally, silica was eluted by treating with concentrated hydrofluoric acid overnight to obtain a carbon structure (referred to as NPGC-N700).
For comparison, a carbon body (represented as SP3-N700) was obtained in the same procedure using commercially available silica gel (Fuji Silysia, P3) as a template.
For these obtained carbon structures, nitrogen adsorption method at 77K, X-ray diffraction method (XRD), diffuse reflection infrared spectroscopy (DRIFT), differential thermal analysis method (TG / DTA), scanning electron microscope ( (FE-SEM) and the like.

From the results of DRIFT, it was found that the sample after hydrofluoric acid treatment was a carbonaceous material containing some surface functional groups, and the results of TG showed that the final product NPGC-N700 had the silica component completely removed. . Further, from the results of XRD, it was found that the final product NPGC-N700 also had a disordered structure similar to the template complex NPGC. FIG. 1 shows nitrogen adsorption isotherms at 77K of NPGC-N700, SP3-N700 and a carbon structure (NPGC-HF) obtained by removing the silica component from the template NPGC with hydrofluoric acid for comparison. The vertical axis in FIG. 1 indicates the amount of nitrogen adsorbed per unit mass (V / mL-STP / g), and the horizontal axis indicates the partial pressure of nitrogen (P / Po). Square marks (■ and □) indicate NPGC-N700 of the present invention, triangle marks (▲ and Δ) indicate SP3-N700 of the comparative example, and circle marks (● and ◯) indicate NPGC-HF of the comparative example. .
Compared with NPGC-HF without naphthalene modification, NPGC-N700 with naphthalene modification greatly increased the amount of adsorption, indicating that a porous structure in which carbon was crosslinked by naphthalene modification was formed. . Moreover, the nitrogen adsorption isotherm of NPGC-N700 was larger than that of SP3-N700 using silica gel as a template.
The results of pore analysis of each obtained carbon structure are shown in Table 1 below.

Here, the surface area (S _BET ) is determined by the BET method, and the total pore volume (V _{0, total} ) is calculated from the nitrogen adsorption amount at P / P ₀ = 0.95, and the mesopore volume (V _{me, BJH} ) by the BJH method. a pore radius _{(R P, BJH) was V 0, total} and _{V me,} than the difference between the _BJH micropore volume of _{(V mi)} was calculated. Compared with NPGC-HF, naphthalene modification increased the specific surface area to close to 800 m ² / g, which was larger than SP3-N700 obtained from the silica template.

Furthermore, the FE-SEM image of NPGC-N700 of this invention and SP3-N700 of a comparative example is shown in the photograph which replaces drawing at FIG. 2 (a) (upper side of FIG. 2) is that of the NPGC-N700 of the present invention, and FIG. 2 (b) (lower side of FIG. 2) is that of the comparative example SP3-N700.
As a result, SP3-N700 is formed by memorizing the shape of the template particles considerably, whereas NPGC-N700 has a carbon plate-like structure. This is thought to be because such a plate-like form could be maintained because a carbon component as a cross-linked product could be inserted between carbon layers.

Further, NPGC-N700 having a specific surface area of 1200 m ² / g could be obtained by the same treatment using NPGC having a specific surface area of 1000 m ² / g obtained separately.
Thus, the specific surface area of the occlusion material having the nanoporous carbon structure of the present invention depends on the specific surface area of NPGC used as a raw material, that is, used as a template, and this is a carbonization treatment method according to the method of the present invention. Is selectively occurring in the pillar part.
Nitrogen adsorption isotherm at 77K using NPGC-N700 having a specific surface area of 1200 m ² / g obtained by this method, NPGC used as a template, and carbon structure not subjected to interlayer expansion treatment (untreated carbon) Was measured. The results are shown in FIG. FIG. 3 shows nitrogen adsorption isotherms at 77 K of NPGC-N700 having a specific surface area of 1200 m ² / g according to the present invention, NPGC used as a template, and a carbon structure not subjected to interlayer expansion treatment (untreated carbon). The vertical axis | shaft of FIG. 3 shows the adsorption amount (V / mL-STP / g) of nitrogen per unit mass, and a horizontal axis shows the partial pressure (P / Po) of nitrogen. Circle marks (● and ◯) indicate NPGC-N700 of the present invention, triangle marks (▲ and △) indicate NPGC used for a mold as a comparative example, and square marks (■ and □) indicate an interlayer as a comparative example. A carbon structure that has not been subjected to expansion treatment (carbon that has not been treated) is shown.
As can be seen from the nitrogen adsorption isotherm in FIG. 3, the amount of nitrogen adsorption of NPGC-N700 of the present invention was higher than that of the template NPGC, while the carbon structure without treatment was almost nonporous. The NPGC-N700 of the present invention has a specific surface area exceeding 1200 m ² / g at the maximum, and there is a possibility that the packing density is increased as compared with ordinary powdered porous carbon. This currently developed material has been found to be superior to commercially available high specific surface area powdered activated carbon (> 2000 m ² / g) when comparing methane storage per unit area.

The present invention provides a novel occlusion material for hydrocarbons such as methane, which is attracting attention as a next-generation energy source. By selectively carbonizing a graphite layer structure with hydroxy hydrocarbons, methane can be obtained. The present invention provides a novel graphite-based hydrocarbon occlusion material modified so as to be maintained in a layer structure suitable for occlusion of hydrocarbons. The carbon-based hydrocarbon storage material of the present invention has a large amount of methane adsorbed per inner surface area, and methane is adsorbed at a high density in the carbon layer structure. For storing such hydrocarbons such as methane, Suitable carbon layer structures are the first disclosed by the present invention. And this invention is characterized by selectively maintaining such a carbon layer structure with a carbonized product.
Examples of the hydrocarbon in the carbon-based hydrocarbon storage material of the present invention include methane, ethane, propane and the like, preferably a hydrocarbon for fuel, more preferably methane.
The carbon-based hydrocarbon storage material of the present invention can be manufactured by the method exemplified above, but the pillar layer for expanding the graphite layer structure and maintaining the expanded layer structure is selectively used. As long as the material is based on the technical idea of the present invention to be maintained in a layer structure suitable for occlusion of hydrocarbons such as methane by substituting with a carbonized product, it is not limited to the production method described above. .

The present invention provides a novel graphite-based occlusion material having a nanoporous carbon structure and a method for producing the same, and the occlusion material having the nanoporous carbon structure of the present invention is used for maintaining the interlayer distance of graphite. The pillar portion is selectively carbonized, and the porous layered compound of the present invention having a thin graphene layer as a wall can improve the surface area and effectively utilize a wide lipophilic surface.
The occlusion material having a nanoporous carbon structure of the present invention maintains most of the lipophilic surface of carbon as it is, and can effectively utilize a large surface area, and is expected from the fields of gas storage, adsorption, catalyst, and the like. . Also, it can store hydrocarbons such as methane at high density, can be produced from graphite in a simple way, and provides new materials for storage, transportation and use of hydrocarbons such as methane To do.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

Preparation of Porous Graphite Composite Material Graphite oxide layered body formed by oxidizing graphite (denoted as G) by the method of Staudenmehr (L. Staudenmier, Ber Deutsche Chem. Ges. 1989, 31, 1481.) (Represented as GO) (Specific surface area 25 m ^{2 /} g) 0.3 g is added little by little in 60 ml of 0.05M aqueous sodium hydroxide solution and dispersed well, and ultrasonic waves are applied for 20 minutes to prepare a uniform dispersion. did.
Next, 0.4 g of hexadecyltrimethylammonium bromide (chemical formula: CH ₃ (CH ₂ ) ₁₅ N ⁺ (CH ₃ ) ₃ .Br) is dissolved in 600 ml of distilled water, and gradually stirred into the above dispersion. After the dropwise addition, the produced precipitate was filtered by suction and washed with water until the pH became neutral. The precipitate thus obtained was filtered off and dried at 60 ° C. overnight to obtain an intercalation compound GO (represented as GOC ₁₆ ) in which hexadecyltrimethylammonium ions were intercalated.
0.32 g of the intercalation compound thus obtained was dispersed in 420 ml of tetraethyl silicate Si (OC ₂ H ₅ ) and reacted at 25 ° C. for 7 days. After the reaction, the produced solid is centrifuged, washed once with 10 ml of ethyl alcohol, left in the atmosphere for 24 hours, and further dried in air at 60 ° C. for 12 hours, so that tetraethyl silicate is inserted between the layers. An intercalation compound (represented as GOC ₁₆ T) was obtained.
Next, the interlayer compound (GOC ₁₆ T) was gradually heated to 550 ° C. in a vacuum, and heated at this temperature for 5 hours. In this way, a porous graphite composite material NPGC having a specific surface area of 870 m ² / g and an average pore diameter of 19.6 nm was obtained.

Preparation of storage material NPGC-N700 The NPGC produced in Example 1 was pretreated in vacuum at 550 ° C. for 2 hours, cooled to room temperature, and then contacted with 50% acetone solution of 2,3-dihydroxynaphthalene without contact with air. And impregnated overnight. Thereafter, acetone was volatilized under reduced pressure, and an esterification reaction was performed at 300 ° C. in a nitrogen atmosphere for 1 hour. Subsequently, excess naphthalene was removed by washing with acetone, dried at 60 ° C. under vacuum overnight, and then carbonized at 700 ° C. for 2 hours in vacuum. Finally, the silica was eluted by treating with concentrated hydrofluoric acid overnight to obtain the target carbon structure (denoted as NPGC-N700).
For the obtained carbon structure NPGC-N700, nitrogen adsorption method at 77K, X-ray diffraction method (XRD), diffuse reflection infrared spectroscopy (DRIFT), differential thermal analysis method (TG / DTA), scanning electron microscope Analysis was performed using (FE-SEM) or the like. The results are shown in FIG. 1 and FIG.

  For comparison, carbon (represented as SP3-N700) was obtained in the same procedure using commercially available silica gel (Fuji Silysia, P3) as a template. As in Example 2, the obtained carbon structure was subjected to nitrogen adsorption method at 77K, X-ray diffraction method (XRD), diffuse reflectance infrared spectroscopy (DRIFT), differential thermal analysis method (TG / DTA), scanning type. Analysis was performed with an electron microscope (FE-SEM) or the like.

Preparation of storage material NPGC-N700 In place of NPGC having a specific surface area of 870 m ² / g, NPGC having a specific surface area of 1000 m ² / g was used, and the target carbon structure (NPGC-N700 and Represent). The specific surface area of the obtained NPGC-N700 was 1200 m ² / g.
The obtained carbon structure NPGC-N700 was measured by a nitrogen isothermal adsorption method at 77K. The results are shown in FIG.

  The present invention provides an occlusion body having a nanoporous carbon structure useful in the fields of gas storage and adsorption of methane gas and the like, and catalyst support, and a method for producing the same, and is attracting attention as a next-generation energy source. It is expected to be used as a catalyst carrier in the field of storage and use of hydrocarbon gases such as methane and in the field of synthetic chemistry, and has industrial applicability.

FIG. 1 shows nitrogen adsorption isotherms at 77K for the NPGC-N700 of the present invention, and the SP3-N700 of the comparative example and the NPGC-HF of the comparative example. The vertical axis in FIG. 1 indicates the amount of nitrogen adsorbed per unit mass (V / mL-STP / g), and the horizontal axis indicates the partial pressure of nitrogen (P / Po). Square marks (■ and □) indicate NPGC-N700 of the present invention, triangle marks (▲ and Δ) indicate SP3-N700 of the comparative example, and circle marks (● and ◯) indicate NPGC-HF of the comparative example. . FIG. 2 shows a scanning electron microscope (FE-SEM) image of the NPGC-N700 of the present invention and the SP3-N700 of the comparative example with a photograph in place of the drawing. 2 (a) (upper side of FIG. 2) is that of the NPGC-N700 of the present invention, and FIG. 2 (b) (lower side of FIG. 2) is that of the comparative example SP3-N700. FIG. 3 shows a nitrogen adsorption isotherm at 77 K of NPGC-N700 of the present invention, NPGC used as a template, and a carbon structure not subjected to interlayer expansion treatment (carbon without polymer treatment). The vertical axis | shaft of FIG. 3 shows the adsorption amount (V / mL-STP / g) of nitrogen per unit mass, and a horizontal axis shows the partial pressure (P / Po) of nitrogen. Circle marks (● and ◯) indicate NPGC-N700 of the present invention, triangle marks (▲ and △) indicate NPGC used for a mold as a comparative example, and square marks (■ and □) indicate an interlayer as a comparative example. A carbon structure that has not been subjected to expansion treatment (carbon that has not been treated) is shown.

Claims (3)

(1) a step of oxidizing graphite to form a graphite oxide, (2) a step of fixing a distance between layer surfaces of the graphite oxide, and (3) a carbon layer having a fixed distance between layer surfaces. A step of adding a hydroxynaphthalene derivative between the carbon layer to maintain the carbon layer, and (4) reacting the material fixing the inter-layer distance with the hydroxynaphthalene derivative added in the step (3). A step, (5) a step of removing the unreacted hydroxynaphthalene derivative , (6) a step of carbonizing the remaining hydroxynaphthalene derivative into a carbonized product, and (7) fixing the distance between the remaining layer surfaces. Having a layer of carbon whose interplanar distance is larger than that of normal graphite, and that these layers are maintained by carbonized products. Method for producing a storage material having a nanoporous carbon structure, characterized by being.   The step of fixing the distance between the layer surfaces includes a sol or a polynuclear metal cation of at least one metal or metalloid compound selected from silicon, aluminum, titanium, zirconium and iron between the graphite oxide layers. 2. The method of claim 1 comprising the steps of intercalating and then heat treating it in an inert atmosphere to form a metal or metalloid oxide. The method according to claim 1 or 2, wherein the hydroxynaphthalene derivative is 2,3-dihydroxylonaphthalene.